This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In previous systems, an object is weighed by attaching the object to a first end of a cable. The cable is pulled upward by routing the cable over a pulley and then wrapping the cable around a drum driven by a drive. The pulley is suspended from a load cell. The weight of the object is determined by analyzing the force applied to the load cell by the pulley. In theory, the force exerted on the pulley by the cable is equal to some multiple of the weight of the object.
Accurately measuring the weight of an object suspended from a cable is useful in a variety of applications. One example is silicon ingot growth operations, where a growing silicon ingot is pulled upward from a crucible of molten silicon. The diameter of the region of the silicon ingot being grown at any instant may be determined based on the density, rate of change of weight, and growth velocity of the ingot. While the density and growth velocity of the ingot are readily determinable to a high degree of accuracy, the rate of change of weight of the ingot is not measurable with a high enough degree of accuracy by previous systems to ensure a correct determination of the ingot diameter. The inherent inaccuracies of previous force measurement systems described above thus render them ill-suited for determining the diameter of a growing silicon ingot based on the weight of the ingot. Known systems therefore utilize more costly and less accurate systems for determining the diameter of the growing silicon ingot.
Moreover, orbital and/or pendular motion of the cable can affect the amount of force exerted on the load cell by the cable and thus affect the force measurement. Orbital and/or pendular motion of the cable can also prevent the ingot from growing in a straight direction and restrict the rate at which the ingot can be rotated.